1. Field of the Invention
The present invention is related to an improvement of a file managing method for a data file, which is directed to a process operation so that only necessary data is effectively derived from a large amount of saved data such as a database.
2. Description of the Related Art
Generally speaking, within a disk apparatus, data are grouped in units of a record, these data are arranged in accordance with a sequential order of the respective records, and the data are arranged in accordance with a definition order of fields within each of the records.
In FIG. 24, there is shown one example of the conventional file managing method in the file management. This drawing illustratively shows such a storage condition that records of a data file to be stored, which are defined from an i-th record up to "n" records have been stored in the disk apparatus.
Japanese Unexamined Patent Application No. Hei 6-176074, laid open in 1994 describes the technical aspect of the related database process operation. In this database process operation, after all of the data are once entered from the disk apparatus into the input/output buffer employed in the database calculating process apparatus, only necessary data are acquired into the internal memory by way of the selecting process operation and the projecting process operation. This technique is intended to effectively utilize the internal memory. However, no detailed explanation is given of the data definition by executing the selecting process operation and the projecting process operation. Also, no description is given of the method for utilizing the data acquired in the internal memory.
In such an above-described storage format in which the data are grouped in the units of the record and the grouped data are stored, even when only a partial field contained in the record is required, all of the records are inputted from the disk apparatus to the input/output buffer, and thereafter a process operation for separating only the necessary records is required.
A process operation for deriving only a partial field corresponds to such a process operation for deriving, for instance, only a name and an address from a staff member database constituted by numbers of staff members, names, ages, addresses, and telephone numbers. As shown in FIG. 25, while a field 17 corresponds to the names and another field 18 corresponds to the addresses, even when only two fields are required, since the data are not stored in the disk apparatus in such a manner that these data are subdivided by every field, all of the fields must be read out from the disk apparatus as to all of the records. Then, the process operation for separating the field 17 and the field 18 must be carried out.
Since the conventional file managing method is arranged in the above-described manner, even when only a partial field contained in the records is needed, all of the records must be entered from the disk apparatus into the input/output buffer. There is a problem. That is, even when the file is formed by separating only the necessary field, since the necessary fields are different, depending upon the use of the file, a process operation for separating only the necessary field must be carried out every time the file is used.